The aim of this study was to investigate the removal efficiency of 17α-methyltestosterone (MT) from aqueous solution by Salvinia cucullata Roxb. ex Bory in an active plant-based reactor with a specific focus on linear regression analysis for the sorption phenomena of MT onto the plant roots. A high performance liquid chromatographic method using UV detection (245 nm) was used to analyse the samples. The batch experiments of the active plant reactor (APR) were established to investigate the ability of Salvinia cucullata to remove MT from the liquid phase. The results revealed that 40% and 60% removal of MT from the liquid phase was observed at 5 min. and at 4 h, respectively. Salvinia cucullata can effectively remove MT from the aqueous solution in APRs. Kinetic studies revealed that the sorption phenomena of MT by Salvinia is best described using a linearized pseudo-second order model. Based on the kinetic parameters, it is likely that during the first 4 h of the contact (t = 0 to t = 4 h) sorption is the major driving mechanism of the disappearance of MT from aqueous solutions. However, at higher MT concentrations, diffusivity of MT has a significant effect on the migration of MT from the bulk stream to the root surface. The isotherm analysis revealed that the sorption kinetics favourably followed pseudo second-order. The results of isotherm analysis have indicated that the sorption of MT onto the root surfaces of Salvinia cucullata was favourable and almost irreversible.
This work aimed to enhance the photocatalytic degradation of methyl orange (MO) by crystallinity transformation of titanium dioxide (TiO2). In addition, the kinetic degradation of MO was determined. To transform its crystallinity, TiO2 was synthesized using a sol–gel method and calcined at between 200°C to 600°C. Calcination at a temperature of 250°C resulted in TiO2 that showed the best performance, corresponding to MO removal of 87% ± 7%. MO removal by TiO2 calcined between 250°C to 400°C was higher than for commercial TiO2 powder (Sigma‐aldrich) (62% ± 4%). TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO, while the specific surface area and surface roughness seemed to play a minor role. The photocatalytic degradation of MO was NaCl‐independent, while the photocatalytic activity increased with decreased pH. Reused TiO2 showed similar photocatalytic degradation of MO compared with pristine TiO2, at 84 ± 2%. The oxidation kinetics of TiO2 calcined at 250°C were fitted to the Langmuir–Hinshelwood model (R2 = 0.9134). The kr and Ks values were 0.027 mg L−1 min−1 and 0.621 L/mg, respectively. Crystallinity transformation was a major factor in the enhancement of photocatalytic degradation of MO.
Practitioner points
Photocatalytic activity of TiO2 depends on calcination temperature, pH, and a number of UVC lamps.
TiO2 with a small crystallite size and high anatase fraction enhanced the photocatalytic degradation of MO.
Pemanfaatan fotokatalis saat ini dikembangkan untuk mendapatkan hasil fotokatalis yang aktif pada sinar tampak sehingga bisa menggunakan sinar matahari yang sudah tersedia di alam sebagai sumber energinya atau dengan menggunakan lampu UV. Proses fotokatalis menjadi alternatif dalam mengolah limbah ataupun fotodegradasi senyawa organik semacam zat organik dengan skala besar serta dengan biaya yang relatif terjangkau. Asam humat merupakan senyawa organik heterogen yang terurai dan dapat mengingat logam berat dan polutan organik yang dapat menyebabkan sejumlah masalah lingkungan atau kesehatan. Oleh karena itu, penelitian ini dilakukan untuk meningkatkan aktivitas fotokatalitik dengan mendegradasikan senyawa organik asam humat dengan bantuan cahaya sinar UVA/UVC dengan penambahan katalis TiO2 dan membandingkan variasi pH serta konsentrasi larutannya.
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